U.S. patent application number 10/280667 was filed with the patent office on 2004-04-29 for color filter panel, manufacturing method thereof, and liquid crystal display including color filter panel.
Invention is credited to Rho, Soo-Guy.
Application Number | 20040080684 10/280667 |
Document ID | / |
Family ID | 32106993 |
Filed Date | 2004-04-29 |
United States Patent
Application |
20040080684 |
Kind Code |
A1 |
Rho, Soo-Guy |
April 29, 2004 |
Color filter panel, manufacturing method thereof, and liquid
crystal display including color filter panel
Abstract
A transflective liquid crystal display includes upper and lower
panels facing each other. On the lower panel, there formed a
plurality of gate lines and a plurality of data lines intersecting
each other to define pixel areas arranged in a matrix. A plurality
of thin film transistors connected to the gate lines and the data
lines and a plurality of pixel electrodes connected to the thin
film transistors are also provided on the lower panel. Each pixel
electrode includes a transparent electrode and a reflecting
electrode with high reflectance having a transmitting window. A
black matrix having apertures opposite the pixel areas and a
plurality of red, green and blue color filters are formed on the
upper panel. Each color filter includes thicker and thinner
portions, and the thicker portion opposite the transmitting
window.
Inventors: |
Rho, Soo-Guy; (Kyungki-do,
KR) |
Correspondence
Address: |
F. Chau & Associates, LLP
Suite 501
1900 Hempstead Turnpike
East Meadow
NY
11554
US
|
Family ID: |
32106993 |
Appl. No.: |
10/280667 |
Filed: |
October 25, 2002 |
Current U.S.
Class: |
349/106 |
Current CPC
Class: |
G02F 1/1362 20130101;
G02F 1/133371 20130101; G02F 1/133514 20130101; G02F 1/133555
20130101 |
Class at
Publication: |
349/106 |
International
Class: |
G02F 001/1335 |
Claims
What is claimed is:
1. A color filter panel for a liquid crystal display comprising: a
substrate; and a color filter formed on the substrate and having a
position dependent thickness.
2. The color filter panel of claim 1, wherein the liquid crystal
display includes a first display area displaying images mainly
using an external light and a second display area displaying images
mainly using a light source provided therein.
3. The color filter panel of claim 2, wherein the thickness of the
color filter in the first display area is smaller than in the
second display area.
4. The color filter panel of claim 1, wherein the color filter
comprises a first portion and a second portion having a thickness
larger than the first portion, and the first portion surrounds the
second portion.
5. The color filter panel of claim 4, further comprising a black
matrix located near edges of the color filter.
6. The color filter panel of claim 5, wherein the color filter
further comprises a third portion thicker than the first portion
and located near edges of the color filter.
7. The color filter panel of claim 6, wherein the third portion of
the color filter overlaps the black matrix at leas in part.
8. The color filter panel of claim 1, further comprising a common
electrode on the substrate.
9. A method of manufacturing a color filter panel for a liquid
crystal display, the method comprising: coating a photosensitive
film comprising a pigment on a substrate; exposing the
photosensitive film to light through at least one mask having a
position-dependent transmissivity for light energy; and forming a
plurality of color filters, each color filter having a
position-dependent thickness by developing the photosensitive
film.
10. The method of claim 9, wherein the at least one mask comprises
first, second and third areas, and the transmissivity for light
energy sequentially increases in the first area, in the second area
and in the third area.
11. The method of claim 10, wherein the second area comprises a
slit pattern or a lattice pattern.
12. The method of claim 9, wherein the photosensitive film is a
negative photosensitive film.
13. The method of claim 12, wherein the photosensitive film further
comprises a monomer, a photopolymerization initiator, and a
binder.
14. The method of claim 13, wherein the insolubility of at least
one portion of the photosensitive film after exposed to light
ranges from 20% to 60%.
15. A transflective liquid crystal display comprising: a first
panel having a color filter having a position-dependent thickness;
and a second panel opposite the first panel, the second panel
comprising field-generating electrode including a transparent
electrode and a reflecting electrode having an opening on the
transparent electrode.
16. The transflective liquid crystal display of claim 15, wherein
the color filter comprises a first portion with a first thickness
and a second portion with a second thickness larger than the first
thickness, and the first portion is opposite the opening.
17. The transflective liquid crystal display of claim 16, wherein
the transparent electrode is located under the reflecting
electrode.
18. The transflective liquid crystal display of claim 17, wherein
the second panel further comprises an insulating layer interposed
between the transparent electrode and the reflecting electrode.
19. The transflective liquid crystal display of claim 18, wherein
the insulating layer comprises an unevenness pattern, and the
reflecting electrode has embossment.
20. The transflective liquid crystal display of claim 15, wherein
the second panel further comprises a gate line, a data line and a
thin film transistor electrically connected to the gate line, the
data line and the transparent electrode.
Description
BACKGROUND OF THE INVENTION
[0001] (a) Field of the Invention
[0002] The present invention relates to a color filter panel, a
manufacturing method thereof, and a liquid crystal display,
especially a transflective liquid crystal display including a color
filter panel.
[0003] (b) Description of Related Art
[0004] A liquid crystal display ("LCD") is one of the most
prevalent flat panel displays, which includes two panels having
field-generating electrodes and a liquid crystal layer interposed
therebetween and controls the transmittance of light passing
through the liquid crystal layer by adjusting voltages applied to
the electrodes to re-arrange liquid crystal molecules in the liquid
crystal layer.
[0005] The most popular one among those LCDs is one having
electrodes on the respective panels and having a plurality of thin
film transistors ("TFTs") for switching the voltages applied to the
electrodes. Generally, the TFTs are provided on one of the two
panels.
[0006] Such LCDs can be classified into two types, one of which is
a transmissive type, displaying images by transmitting light from a
specific light source called backlight through the liquid crystal
layer, and the other of which is a reflective type, displaying
images by reflecting external light such as natural light into the
liquid crystal layer using a reflector of the LCD. Nowadays, a
transflective type LCD operating in both a transmissive mode and a
reflective mode is being developed.
[0007] On the other hand, a conventional LCD is equipped with red,
green and blue color filters for realizing color displays. Color
image is obtained by controlling the light transmittance passing
through the respective red, green and blue color filters. The
impression of colors among display devices is different due to the
characteristics of the display devices, and the difference in the
color impressions among the display devices is corrected or
obtained by adjusting the thickness of the color filters or the
density of the pigment distributed in the color filters.
[0008] The transflective type LCD shows non-uniform color
reproducibility between in the transmissive mode and in the
reflective mode since the number of the light passage through the
color filters is different, which results in deterioration of the
display characteristic. That is, the light in the transmissive mode
passes the liquid crystal layer and the color filter only once to
reach a user's eye, while the light in the reflective mode passes
twice the liquid crystal layer and the color filter. Therefore, the
impressions of the color in the two modes become different.
SUMMARY OF THE INVENTION
[0009] A liquid crystal display is provided, which includes: a
substrate; and a color filter formed on the substrate and having a
position-dependent thickness.
[0010] The liquid crystal display preferably includes a first
display area displaying images mainly using an external light and a
second display area displaying images mainly using a light source
provided therein. The thickness of the color filter in the first
display area is preferably smaller than in the second display
area.
[0011] According to an embodiment of the present invention, the
color filter includes a first portion and a second portion having a
thickness larger than the first portion, and the first portion
surrounds the second portion.
[0012] Preferably, the color filter panel further includes a black
matrix located near edges of the color filter and a third portion
thicker than the first portion and located near edges of the color
filter. The third portion of the color filter preferably overlaps
the black matrix at leas in part.
[0013] According to an embodiment of the present invention, the
color filter panel further includes a common electrode on the
substrate.
[0014] A method of manufacturing a color filter panel for a liquid
crystal display is provide, which includes: coating a
photosensitive film comprising a pigment on a substrate; exposing
the photosensitive film to light through at least one mask having a
position-dependent transmissivity for light energy; and forming a
plurality of color filters, each color filter having a
position-dependent thickness by developing the photosensitive
film.
[0015] According to an embodiment of the present invention, the at
least one mask comprises first, second and third areas, and the
transmissivity for light energy sequentially increases in the first
area, in the second area and in the third area. The second area
preferably includes a slit pattern or a lattice pattern.
[0016] According to an embodiment of the present invention, the
photosensitive film is a negative photosensitive film, and further
includes a monomer, a photopolymerization initiator, and a binder.
Preferably, the insolubility of at least one portion of the
photosensitive film after exposed to light ranges from 20% to
60%.
[0017] A transflective liquid crystal display is provided, which
includes: a first panel having a color filter having a
position-dependent thickness; and a second panel opposite the first
panel, the second panel comprising a field-generating electrode
including a transparent electrode and a reflecting electrode having
an opening on the transparent electrode.
[0018] Preferably, the color filter comprises a first portion with
a first thickness and a second portion with a second thickness
larger than the first thickness, and the first portion is opposite
the opening.
[0019] According to an embodiment of the present invention, the
transparent electrode is located under the reflecting electrode,
and the second panel further includes an insulating layer
interposed between the transparent electrode and the reflecting
electrode. The insulating layer preferably includes an unevenness
pattern.
[0020] According to an embodiment of the present invention, the
second panel further comprises a gate line, a data line and a thin
film transistor electrically connected to the gate line, the data
line and the transparent electrode.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The above and other objects and advantages of the present
invention will become more apparent by describing preferred
embodiments thereof in detail with reference to the accompanying
drawings in which:
[0022] FIG. 1 is a layout view of a TFT array panel for a
transflective LCD according to an embodiment of the present
invention;
[0023] FIG. 2 is a sectional view of an LCD including the TFT array
panel shown in FIG. 1 taken along the line II-II';
[0024] FIGS. 3A-3C are sectional views of a color filter panel of a
transflective LCD in the steps of a manufacturing method according
to an embodiment of the present invention;
[0025] FIG. 4 is a graph showing the remaining thickness of
photoresist films for red, green, and blue color filters as
function of exposure energy flux;
[0026] FIG. 5 is a graph showing the transmittance of red, green,
and blue color filters having different thicknesses as function of
the wavelength of light;
[0027] FIG. 6 is a graph showing the color coordinates of red,
green and blue color filters having different thicknesses;
[0028] FIGS. 7A, 8A, 9A, 10A, 11A and 12A are layout views of a TFT
array panel of a transflective LCD in the steps of a manufacturing
method according to an embodiment of the present invention;
[0029] FIG. 7B is a sectional view of the TFT array panel shown in
FIG. 7A taken along the line VIIB-VIIB';
[0030] FIG. 8B is a sectional view of the TFT array panel shown in
FIG. 8A taken along the line VIIIB-VIIIB', which is the next step
of FIG. 7B;
[0031] FIG. 9B is a sectional view of the TFT array panel shown in
FIG. 9A taken along the line IXB-IXB', which is the next step of
FIG. 8B;
[0032] FIG. 10B is a sectional view of the TFT array panel shown in
FIG. 10A taken along the line XB-XB', which is the next step of
FIG. 9B;
[0033] FIG. 11B is a sectional view of the TFT array panel shown in
FIG. 11A taken along the line XIB-XIB', which is the next step of
FIG. 10B; and
[0034] FIG. 12B is a sectional view of FIG. 12A along the line
XIIB-XIIB', which is the next step of FIG. 11B.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] The present invention now will be described more fully
hereinafter with reference to the accompanying drawings, in which
preferred embodiments of the invention are shown. This invention
may, however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein. In the
drawings, the thickness of layers and regions are exaggerated for
clarity. Like numerals refer to like elements throughout. It will
be understood that when an element such as a layer, film, region,
substrate or panel is referred to as being "on" another element, it
can be directly on the other element or intervening elements may
also be present. In contrast, when an element is referred to as
being "directly on" another element, there are no intervening
elements present. Then, a color filter panel, a transflective
liquid crystal display, and a manufacturing method thereof
according to embodiments of the present invention will be described
with reference to the drawings.
[0036] First, a structure of an LCD according to an embodiment of
the present invention is described in detail with reference to
FIGS. 1 and 2.
[0037] FIG. 1 is a layout view of a TFT array panel for a
transflective LCD according to an embodiment of the present
invention, and FIG. 2 is a sectional view of an LCD including the
TFT array panel shown in FIG. 1 taken along the line II-II'.
[0038] As shown in FIGS. 1 and 2, an LCD according to an embodiment
of the present invention includes lower and upper panels 400 and
600 facing each other and a liquid crystal layer interposed
therebetween.
[0039] A plurality of gate lines 22 and a plurality of data lines
62, which intersect each other to define a plurality of pixel areas
P arranged in a matrix, are formed on the lower panel 400. In each
pixel area P, a TFT connected to the gate and the data lines 22 and
62, and a pixel electrode electrically connected to the TFT are
provided. Each pixel electrode includes a transparent electrode 82
preferably made of transparent conductive film and a reflecting
electrode 92 preferably made of reflective conductive film and
having a transmitting window 96. An area occupied by the
transmitting window 96 is referred to as a "transmissive area" T,
while the remaining area of the pixel area P is referred to as a
"reflective area" R hereinafter. In addition, areas of the lower
panel corresponding to the transmissive area T and the reflective
area R are referred to as the same names and numerals
hereinafter.
[0040] A black matrix 120 having openings corresponding to the
pixel areas P is formed on the upper panel 600, and red, green or
blue color filters 130, which are covered with a common electrode
140, are formed on each pixel area P. For each of the red, green
and blue color filters 130, a portion 132 located in the reflective
area R has a thickness different from another portion 134 in the
transmissive area. In this embodiment, the portion 132 in the
transmissive area T has a larger thickness than the portion 134 in
the reflective area R.
[0041] Here, the reflective area R is mainly used for displaying
images utilizing the light reflected from the reflecting electrode
92, while the transmissive area T is mainly used for displaying
images utilizing the light from a backlight, its own light
source.
[0042] In the LCD according to this embodiment of the present
invention, the images in the transmissive area T are generated by
the light which passed through the color filter 130 only once,
while those in the reflective area R are generated by the light
which reaches the reflecting electrode 92 after passing through the
color filter 130 once and then passes through the color filter 130
again after reflected by the reflecting electrode 92. Since the
thickness of the color filter 130 in the reflective area R is
smaller than that in the transmissive area T, two lights in the two
areas T and R experience the color filter 130 almost in the same
degree. Accordingly, the color reproduction properties for two
areas T and R can be made to be equalized, thereby improving the
display characteristic of the LCD.
[0043] Next, the structure of the lower panel 400 of the LCD
according to the embodiment of the present invention is described
in more detail.
[0044] The lower panel 400 includes an insulating substrate 10. A
plurality of gate lines 22 extending substantially in a transverse
direction are formed on the substrate 10. Each gate line 22 has a
single-layered structure preferably made of a material having low
resistivity such as silver, silver alloy, aluminum or aluminum
alloy. Alternatively, each gate line 22 has a multiple-layered
structure including a layer or layers made of the above listed
materials, and preferably including at least one layer having good
contact characteristic with another material. A portion 24 near one
end of each gate line 22 transmits gate signals from an external
device to the gate line 22, and a plurality of branches 26 of each
gate line 22 serve as gate electrodes 26 of TFTs.
[0045] A gate-insulating layer 30 preferably made of silicon
nitride (SiNx) or the like covers the gate lines 22.
[0046] A plurality of semiconductor islands 40 preferably made of
hydrogenated amorphous silicon is formed on the gate insulating
layer 30 opposite the gate electrode 26, and a plurality of pairs
of ohmic contacts 55 and 56 preferably made of silicide or n+
hydrogenated amorphous silicon heavily doped with n type impurity
are formed on the semiconductor islands 40. One 55 of each pair of
ohmic contacts 55 and 56 is separated from the other 56 with
respect to corresponding one of the gate lines 22.
[0047] A plurality of data lines 62 and a plurality of drain
electrodes 66 are formed on the ohmic contacts 55 and 56 and the
gate insulating layer 30. The data lines 62 and the drain
electrodes 66 preferably include a conductive material having low
resistivity such as aluminum or silver. The data lines 62 extend
substantially in a longitudinal direction to intersect the gate
lines 22. A plurality of branches 65 of the data lines 62 extend to
the upper surfaces of the ones 55 of the respective pairs of the
ohmic contacts 55 and 56 to form a plurality of source electrodes
65 of the TFTs. A portion 68 near one end of each data line 62
transmits data signals from an external source to the data line 62.
The drain electrodes 66 of the TFTs are separated from the data
lines 62 and located on the others 56 of the respective pairs of
the ohmic contacts 55 and 56 opposite the source electrodes 65 with
respect to the corresponding gate electrodes 26.
[0048] A passivation layer 70 preferably made of silicon nitride or
organic material with good planarizability is formed on the data
lines 62, the drain electrodes 66 and portions of the semiconductor
islands 40 without being covered by the data lines 62 or the drain
electrodes 66.
[0049] A plurality of contact holes 76 and 78 respectively exposing
the drain electrodes 66 and the end portions 68 of the data lines
62 are formed through the passivation layer 70, and a plurality of
other contact holes 74 exposing the end portions 24 of the gate
lines 22 are provided in the passivation layer 70 and the
gate-insulating layer 30.
[0050] A plurality of transparent electrodes 82 electrically
connected to the drain electrodes 66 via the contact holes 76 are
formed on the passivation layer 70 in the pixel areas P. In
addition, a plurality of contact assistants 84 and 88 respectively
connected to the end portions 24 of the gate lines 22 via the
contact holes 74 and to the end portions 68 of the data lines 62
via the contact holes 78 are formed on the passivation layer 70.
The transparent electrodes 82 and the contact assistants 84 and 88
are preferably made of transparent conductive material such as ITO
(indium tin oxide) or IZO (indium zinc oxide).
[0051] An interlayer-insulating layer 34 is formed on the
transparent electrodes 82. The interlayer insulating layer 34 is
preferably made of silicon nitride, silicon oxide, or organic
insulating material and has a plurality of contact holes 36
exposing the transparent electrodes 82 at least in part.
[0052] A plurality of reflecting electrodes 92 are formed on the
interlayer insulating layer 34. Each reflecting electrode 92 is
connected to the associated transparent electrode 82 via the
appropriate contact hole 36 and has a transmitting window 96. The
reflecting electrodes 92 are preferably made of a conductive film
having high reflectance such as aluminum, aluminum alloy, silver,
silver alloy, molybdenum, or molybdenum alloy. Here, it is
preferable that the interlayer-insulating layer 34 has a rough top
surface so as to make the surfaces of the reflecting electrodes 92
to become uneven, thereby increasing the reflectance of the
reflecting electrodes 92. A pair of one of the reflecting
electrodes 92 and the related transparent electrode 82 form a pixel
electrode. The shapes of the transmitting windows 96 of the
reflecting electrodes 92 are various, and the number of the
transmitting windows 96 in a pixel area is not limited to one but
may be equal to or more than two.
[0053] Each pixel electrode 82 and 92 overlaps one of the gate
lines 22 called a previous gate line 22, which transmits a gate
signal to TFTs of a pixel row adjacent thereto, to form a storage
capacitor. If the storage capacitance of the storage capacitor is
too small, another storage capacitor formed of a conductor made of
the same layer as the gate lines 22 and the pixel electrode 82 and
92 or another conductor connected to the pixel electrode 82 and 92
can be added.
[0054] Each reflecting electrode 92 overlaps the data lines 62
adjacent thereto to maximize the aperture ratio of each pixel area
P.
[0055] Now, a manufacturing method of a color filter panel and a
TFT array panel of an LCD according to an embodiment of the present
invention is described in detail.
[0056] First, a manufacturing method of a color filter panel
according to an embodiment of the present invention is described in
detail with reference to FIGS. 3A-3D.
[0057] As shown in FIG. 3A, a black matrix 120 is formed by
depositing the upper surface of an upper insulating substrate 100
with a material having good light-blocking characteristic and
patterning the deposited material through photolithography using a
photomask.
[0058] Then, as shown in FIG. 3B, a negative photosensitive film
135 is coated on the upper surface of the upper insulating
substrate 100. The negative photosensitive film 135 is a
water-insoluble dispersion solution containing a photopolymerizable
photosensitive composition including photopolymerization
initiators, monomers, binders, etc., and one of red, green and blue
pigments. Thereafter, the photosensitive film 135 is exposed to
light through a mask 200 which can vary the energy absorbed by the
photosensitive film 135 for different areas A, B and C.
[0059] The photopolymerization of the exposed portions of the
negative photosensitive film 135 results in insolubility of the
portions for an alkali developing solution. More specifically, the
photopolymerization initiators are activated to free-radical
initiators upon exposure to the light, the free-radical initiators
induce the monomers to generate free-radical monomers, and then the
radical monomers are polymerized to polymers through chain-reaction
polymerization. As a result, the exposed portions of the
photosensitive film 135 become insoluble.
[0060] In this embodiment, the thickness of the photosensitive film
135 after developed is different depending on the position by
differentiating the degrees of the insolubility of the
photosensitive film 135 to the developing solution depending on the
position, using a mask, which can vary the exposure energy absorbed
by the photosensitive film 135. This is to be described in detail
with reference to FIG. 4.
[0061] FIG. 4 is a graph showing the thickness of remaining
portions of photosensitive films for red, green and blue color
filters as function of the exposure energy flux.
[0062] The curves shown in FIG. 4 illustrate small variation of the
thickness of the remaining portions for the exposure energy flux in
a range of 30-170 mJ/cm.sup.2, while illustrate drastic change for
the exposure energy flux in a range of 10-30 mJ/cm.sup.2. That is,
the steep variation of the dissolubility of the binders to the
developing solution depending on the exposure energy causes the
drastic change of the degree of the photopolymerization in the
latter range. This means that the thickness of the remaining
portions of the photosensitive films can be easily adjusted by
controlling the exposure energy flux in this range. Changing the
kinds of the monomers and the photopolymerization initiators and
the mixture ratio thereof can control the slope of the thickness of
the remaining portions as function of the exposure energy flux.
[0063] Here, the initial energy is almost fully transferred to
portions of the photosensitive film 135 in the area A, while the
initial energy is almost fully blocked not to reach portions in the
area B. Portions of the photosensitive film 135 in the area C
receive part of the initial energy, flux of which ranges from 10
mJ/cm.sup.2 to 30 mJ/cm.sup.2.
[0064] The area C can be obtained by using a mask 200 having a
translucent portion with a slit pattern or a lattice pattern. When
using a slit pattern, it is preferable that the width of the slits
or the distance between the slits is smaller than the resolution of
an exposer used in this step. Alternatively, the mask 200 with a
translucent portion is obtained by making the thickness of a layer
thereon to be different depending on the position or by using a
plurality of layers having different transmissivity.
[0065] In this embodiment, when exposed to light through the mask
200, the portions in the area C are polymerized in part, preferably
20-60%.
[0066] The photosensitive film 135 is developed using an alkali
solution. Then, as shown in FIG. 3C, a color filter 130 having two
portions 132 and 134 with different thickness is obtained.
[0067] An array of color filters is obtained by repeatedly
performing these steps for red, green and blue color filters.
[0068] Finally, a common electrode 140 preferably made of a
transparent conductive material such as ITO and IZO is formed on
the color filter 130 and the black matrix 120.
[0069] Although this embodiment of the present invention uses the
single mask 200 which can give the different exposure energies
depending on the positions, another embodiment uses two or more
masks, respective masks giving different exposure energies.
[0070] According to another embodiment of the present invention,
edge portions of the color filter 130 overlapping the black matrix
120 has substantially the same thickness as the portion 132, as
shown in FIG. 3D. That is, the area A is located at a position
between the areas B and C as well as at a position corresponding to
a transmitting window. This makes the thickness of the color filter
135 in the area C to be uniform, and prevents the edges of the
color filter 132 from being detached when developing.
[0071] Next, it will be described the transmittance and the color
coordinates of red, green and blue color filters with different
thickness between in a transmissive area T and in a reflective area
R.
[0072] FIG. 5 is a graph showing the transmittance of red, green
and blue color filters having difference thickness according to an
embodiment of the present invention as function of the wavelength
of incident light for a transmissive area T and a reflective area
R, and FIG. 6 is a graph showing the color coordinates of red,
green and blue color filters having difference thickness according
to the embodiment of the present invention.
[0073] The thickness of the color filters was about 0.8 microns and
0.4 microns in the transmissive area T and the reflective area R,
respectively. The color reproducibility obtained by adjusting the
thickness of the color filters in the range of about 0.2-2 microns
was about 16%. In FIG. 5, the solid lines indicate the
transmittances of the red, green and blue color filters in the
transmissive area T, while the dotted lines indicate those in the
reflective area R. In FIG. 6, "T" indicates the color coordinates
in the transmissive area T, and "R" indicates those in the
reflective area R.
[0074] As shown in FIG. 5, it was observed that the transmittance
of each color filter was different in the transmissive area T and
in the reflective area R, and this is considered to be resulted
from the thickness difference in the two area T and R. Accordingly,
the appropriate adjustment of the color filters enables to realize
the different color reproducibility in the areas T and R.
[0075] As shown in FIG. 6, the color reproducibility in the
transmissive area T is about 16%, while that in the reflective area
is about 8%.
[0076] The color reproducibility of a display device based on the
NTSC (National Television System Committee) is defined as the ratio
of the area of the triangle including segments connecting the
monochrome points for red, green and blue colors of the display in
the CIE (Commission Internationale de l'Eclairage) color coordinate
system with respect to a standard area suggested by the NTSC.
[0077] Now, a manufacturing method of a TFT array panel according
to an embodiment of the present invention is described in detail
with reference to FIGS. 7A-12B as well as FIGS. 1 and 2.
[0078] First, as shown in FIGS. 7A and 7B, a conductive material
having low resistivity is deposited on an upper surface of a lower
glass substrate 10 and patterned to form a plurality of gate lines
22 substantially extending in a transverse direction and including
a plurality of gate electrodes.
[0079] Next, triple layers of a gate insulating layer 30 preferably
made of silicon nitride, a semiconductor layer preferably made of
amorphous silicon, and a doped amorphous silicon layer are
deposited in sequence. The upper two layers of the semiconductor
layer and the doped amorphous silicon layer are patterned in
sequence using a photomask to form a plurality of semiconductor
islands 40 and a plurality of doped amorphous silicon islands 50
thereon opposite the gate electrode 24, as shown in FIGS. 8A and
8B.
[0080] Subsequently, a conductive layer is deposited and patterned
using photolithography to form a plurality of data lines 62
intersecting the gate lines 22 and a plurality of drain electrodes
62. Each data line 62 includes a plurality of source electrodes 65
extending to an upper surface of the corresponding doped amorphous
silicon islands 50. The drain electrodes 66 separated from the data
lines 62 and opposite to the related source electrodes 65 with
respect to the gate electrodes 26.
[0081] Thereafter, as shown in FIGS. 9A and 9B, portions of the
doped amorphous silicon islands 50, which are not covered with the
data lines 62 and the drain electrodes 66, are removed so that each
doped amorphous silicon island 50 is divided into two ohmic
contacts 55 and 56 with respect to the gate electrode 26, and
portions of the semiconductor island 40 under the removed portions
of the doped amorphous silicon island 50 are exposed. It is
preferable to perform oxygen plasma treatment to stabilize the
surface of the exposed portions of the semiconductor islands
40.
[0082] Succeedingly, a passivation layer 70 is formed by deposition
of organic material with low dielectric constant and good
planarizability or insulating material such as silicon nitride.
Thereafter, as shown in FIGS. 10A and 10B, the passivation layer 70
and the gate insulating layer 30 is patterned by dry etch using
photolithography to form a plurality of contact holes 74, 76 and 78
exposing end portions 24 of the gate lines 22, the drain electrodes
66 and end portions 68 of the data lines 62, respectively.
[0083] Subsequently, as shown in FIGS. 11A and 11B, an ITO layer or
an IZO layer is deposited and patterned using a photomask to form a
plurality of transparent electrodes 82 connected to the associated
drain electrodes 66 via the contact holes 76, and a plurality of
contact assistants 86 and 88 connected to the end portions 24 of
the gate lines 22 and the end portions 68 of the data lines 62 via
the contact holes 74 and 78, respectively.
[0084] Now, as shown in FIGS. 12A and 12B, an interlayer insulating
layer 34 having a plurality of contact holes 36 exposing the
transparent electrodes 82 is formed by depositing organic
insulating material and patterning it using photolithography. An
unevenness pattern is preferably provided on the
interlayer-insulating layer 34.
[0085] Finally, as shown in FIGS. 1 and 2, a plurality of
reflecting electrodes 92, each having a transmitting window 96, are
formed by depositing and patterning a conductive layer with high
reflectance such as aluminum, silver, or molybdenum. The reflecting
electrode 92 preferably has embossment due to the unevenness
pattern of the underlying interlayer insulating layer 34, which
enhances reflectance of the reflecting electrode 92.
[0086] While the present invention has been described in detail
with reference to the preferred embodiments, it is to be understood
that the invention is not limited to the disclosed embodiments,
but, on the contrary, is intended to cover various modifications
and equivalent arrangements included within the sprit and scope of
the appended claims.
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